Temperature induced in-gap states in the band structure and the insulator-metal transition in LaCoO3

2010/05/11 by S. Ovchinnikov, Ovchinnikov, S., Yu. Orlov +5
Physics and Astronomy · #FOS: Physical sciences #Strongly Correlated Electrons (cond-mat.str-el) #cond-mat.str-el

paper · pdf · doi:10.48550/arxiv.1005.1732

arxiv created 2010/05/11 · arxiv updated 2010/05/12

Abstract

For many years a spin-state transition at T ≈ 100 K and insulator - metal transition (IMT) at T_IMT ≈ 600 K in LaCoO₃ remains a mystery. Small low-spin - high-spin spin gap Δ_S = E( HS ) - E( LS ) ∼ 100 K results in the spin-state transition. The large charge gap 2E_a ≈ 2300 K (E_a is the activation energy) vs. Δ_S and T_IMT implies that LaCoO₃ is not a simple narrow-gap semiconductor. Here we explain both the spin-state and IMT on the same footing. We obtain strong temperature dependent band structure in LaCoO₃ by the LDA+GTB method that incorporates strong electron correlations, covalence and spin-orbital interaction exactly inside the CoO₆ cluster and the interclaster hopping between different multielectron configurations by perturbation theory for Hubbard X-operators.

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